JP2594120B2 - Conductive resin composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a conductive resin composition used for a conductive roll such as a charging roll and a developing roll of an electrophotographic copying machine.

[Conventional technology]

As shown in FIG. 1, a conductive roll such as a charging roll, which is an electronic component of an electrophotographic copying machine, is usually composed of a metal shaft 4 and a conductive polymer layer 5 formed on the outer peripheral surface thereof. ing. As the conductive polymer composition forming the conductive polymer layer 5, a conductive resin composition in which a conductive agent is mixed in a thermosetting resin such as an epoxy resin or a phenol resin is generally known. .

[Problems to be solved by the invention]

However, since the conductive resin composition contains a large amount of a conductive agent in the thermosetting resin, the cured product is brittle, and has a significantly different coefficient of thermal expansion from the metal shaft 4. Therefore, when forming a conductive polymer layer using the same, it occurs at the time of forming the conductive polymer layer,
Cracks occur in the formed conductive polymer layer due to distortion of the resin due to a difference in thermal expansion coefficient and a heat cycle during use. Therefore, the conventional conductive resin composition,
When applied to a product used in an area where the temperature difference is severe such as summer and winter, or a product used in a cold region or a very hot region, an effect that is sufficiently satisfactory cannot be obtained.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a conductive resin composition that does not cause cracks in a cured product thereof even in a region having a large temperature difference, a cold region, or a very hot region.

[Means for solving the problem]

In order to achieve the above object, the conductive resin composition of the present invention has a configuration in which elastomer particles having a particle size of 500 μm or less are dispersed in a thermosetting resin matrix component containing a conductive agent.

[Action]

That is, the present inventors have conducted a series of studies for the purpose of preventing the occurrence of cracks in a cured product of the conductive resin composition without affecting the conductivity of the conductive resin composition. It was determined that when the particles were dispersed in the composition, the elastomer particles could absorb the strain and prevent cracking. Further, as a result of further studies, mainly on the above-mentioned elastomer particles, it was found that the use of particles having a particle size of 500 μm or less would prevent the occurrence of cracks without affecting conductivity. Reached.

The conductive resin molded article of the present invention is obtained by using a thermosetting resin matrix component, a conductive agent, and elastomer particles having a particle size of 500 μm or less.

The thermosetting resin of the thermosetting resin matrix component is not particularly limited, but epoxy resins, phenol resins, and the like conventionally used from the viewpoint of dimensional stability and moldability are used.

Examples of the conductive agent dispersed in the matrix component include metal powders such as carbon black, copper powder and silver powder, and these may be used alone or in combination.

The mixing ratio of the thermosetting resin and the conductive agent is 100 parts by weight of the thermosetting resin (hereinafter abbreviated as “parts”).
It is preferably set in the range of 300 parts, and in particular, the cured product of the conductive resin composition using the semi-conductive region (10 ⁶ to 10 ¹¹
Ω · cm) is preferably around 200 parts.

Elastomer particles dispersed in the matrix component together with the conductive agent include rubber materials such as natural rubber (NR), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), polystyrene, Examples include thermoplastic resin materials such as polyolefin, polyurethane, polyester, and polyvinyl chloride (PVC), which are used alone or in combination. It is necessary to use those elastomer particles having a particle diameter of 500 μm or less by, for example, freeze-pulverization (an operation of immersing the elastomer particle material in liquid nitrogen and pulverizing while supplying liquid nitrogen). Especially, particle size 100μm
The following fine particles are preferred. That is, the particle size is 500 μm
When using more than one, in addition to having an effect on the conductivity, the dispersion state of the elastomer particles to the thermosetting resin matrix component becomes worse, and the strength of the conductive resin composition cured body varies, and This is because the strength of the entire cured body also decreases. This is considered to be due to the fact that the elastomer particles having a particle size of 500 μm or less have substantially the same particle size as the other additives, and thus have a good dispersion state in the thermosetting resin matrix component. In particular, when the conductive polymer layer 5 (see FIG. 1) of the conductive roll is formed using the conductive resin composition of the present invention, when the conductive roll is a charging roll or the like, the conductive polymer It is preferable to use a resin composition that can set the layer 5 to a semiconductive region and that can be configured to exhibit an affinity for a copying toner of an electrophotographic copying machine. As the resin composition having a high affinity for the toner and having conductivity in the semiconductive region, a resin composition in which the matrix component is a phenol resin and the elastomer particles are polyester elastomer particles is preferable. The polyester elastomer particles have an electric resistance of ^{108 to 11} Ω ·
When the conductive polymer layer is set as a semiconductive region for an electrophotographic copying machine as compared to other elastomer particles, since the conductive polymer layer is in a semiconductive region with cm and has good compatibility with copying toner. Ideal for

The mixing ratio of the elastomer particles is preferably set in the range of 2 to 40% by weight in the mixture of the thermosetting resin and the conductive agent, and in particular, the cured product of the conductive resin composition of the present invention is used as a semiconductive region. Is preferably 2 to 10% by weight. That is, if the mixing ratio is less than 2% by weight, a sufficient effect of preventing cracking will not be obtained, and if it exceeds 40% by weight, the cured product of the conductive resin composition tends to be too soft.

If necessary, besides the above raw materials, glass fiber,
An additive such as a reinforcing material such as carbon fiber or a processing aid may be appropriately compounded.

The conductive resin composition of the present invention is produced, for example, as follows. That is, first, the elastomer particle material is pulverized to a particle diameter of 500 μm or less by freeze pulverization or the like. The desired conductive resin composition can be obtained by appropriately mixing and kneading the above-mentioned elastomer particles pulverized to a particle size of 500 μm or less and other component materials, and then pulverizing the mixture.

The conductive resin composition thus obtained is formed, for example, by a conductive polymer layer or the like on the surface of a conductive roll by extrusion molding or the like, and can cope with a large change in environmental temperature without causing cracks or the like. Become like

〔The invention's effect〕

As described above, the conductive resin composition of the present invention contains elastomer particles having a specific particle size in the resin matrix. The strain is respired by the elastomer particles and does not crack. In addition, since the above-mentioned elastomer particles have a specific particle size, their use does not affect the electrical properties such as conductivity. Therefore, this conductive resin composition is suitable as a material for forming a conductive polymer layer on a surface layer of a charging roll, a developing roll, and the like of an electrophotographic copying machine.

 Next, examples will be described together with comparative examples.

[Examples 1 to 4, Comparative Examples 1 to 4] First, as elastomer particles, a polyester elastomer (Perprene P type, manufactured by Toyobo Co., Ltd.) and NB
R is cooled and pulverized using a Hosokawa Micron Linrex Mill (manufactured by Hosokawa Seisakusho Co., Ltd.).
Two types having a size of 0 μm or less were prepared. Then, the respective component raw materials shown in Table 1 described later were mixed, kneaded and crushed in the mixing ratio shown in the same table to obtain a desired conductive resin composition. The PERPEN P type manufactured by Toyobo Co., Ltd. is obtained by copolymerizing an aromatic polyester in the hard segment and an aromatic polyether in the soft segment.

The powdery conductive resin composition obtained by the above Examples and Comparative Examples was compression-molded to produce a plate-shaped conductive resin molded product. The plate-shaped conductive resin molded product was bonded to a plate-shaped metal piece to produce a test piece 2 as shown in FIG. In the figure, reference numeral 1 denotes a plate-shaped metal piece made of mesh material (SUM) + nickel plating, and 3 denotes a conductive resin molded product which is adhered with a conductive epoxy resin adhesive. Next, using this test piece 2, -30 ° C. →
A heat cycle test was performed with + 80 ° C. → −30 ° C. as one cycle, and the number of cycles at which cracks occurred in the conductive resin molded article 3 was observed. In addition, 6
Measure the electrical resistance (Rv) at each location and measure the degree of variation R
The average value x was determined and is shown in Table 2. On the other hand, only a plate-shaped conductive resin molded product was used as a test piece, and its flexural fracture strength, fracture strain, and flexural modulus were measured in accordance with JIS-K-7203, and the results are shown in the same table.

From the results in Table 2, in the example, the conductive resin molded product 3
Although it contains a large amount of a conductive agent, it has endured a heat cycle test four times or more. On the other hand, in Comparative Example 1 in which a large amount of the conductive agent was contained, cracks occurred during the first heat cycle test. In Comparative Example 3 in which the amount of the conductive agent was significantly reduced, the performance was equivalent to that of the example. Also, when the example is compared with Comparative Example 1 containing an equal amount of a conductive agent, it can be seen that the electrical properties are almost the same, but the mechanical properties such as bending strength and breaking strain are remarkably excellent. In Comparative Examples 2 and 3, although the amount of the conductive agent was reduced and the mechanical characteristics were improved, the insulating properties were high and the conductive agents were out of the semiconductive region.

In Comparative Example 4 using polyester elastomer particles having a particle size of 550 μm, the electrical resistance is almost the same as that of the example product, but the degree of variation (R) in the electrical resistance is significantly large. Also, the mechanical properties are inferior to those of the example product.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing the configuration of a general conductive roll, and FIG. 2 is a perspective view of a test piece used in Examples and Comparative Examples.

Claims (1)

(57) [Claims] 1. A conductive resin composition comprising elastomer particles having a particle size of 500 μm or less dispersed in a thermosetting resin matrix component containing a conductive agent.